Monosodium urate (MSU) crystals activate monocytes via the Toll-like receptor (TLR) pathway and the inflammasome. Binding to TLR and CD14 promotes phagocytosis and cell activation through MYD88-dependent signalling mechanisms. In the cytosol, MSU crystals induce the formation of the NALP-3 (NACHT, LRR, and pyrin domain-containing-3) inflammasome and lead to caspase-1 processing of pro-IL-1β. Activation of the endothelium by IL-1β increases trafficking of neutrophils to the inflammatory site. ASC, apoptosis-associated speck-like protein containing a caspase-associated recruitment domain; IL, interleukin; NF-κB, nuclear factor-kappa-B.